1. Field of the Invention
The present invention relates to fuel return systems, and, in particular, to valves in fuel return systems.
2. Description of Related Art
Traditional ecology fuel return systems can be found in gas turbine engines, for example, in gas turbine engines used in aircraft. A traditional ecology fuel return system is generally configured to remove a certain known amount of jet fuel from the engine's fuel manifolds, for example, fuel nozzle/injector manifolds, engine fuel supply lines, and the like, upon engine shutdown. Upon engine startup, the jet fuel from the ecology fuel return system is returned to the engine's fuel pump inlet via an ejector pump to be injected in the combustor thus providing stable engine idle operations. Ecology fuel return systems can minimize the amount of fuel left over in the engine's fuel system after engine shutdown, thus minimizing the possibility for any liquid fuel and/or any gaseous fuel vapor leaks into the environment. In addition, ecology fuel return systems can also prevent any potential coking of the fuel manifold nozzles and injectors by scavenging the “left-over” liquid fuel from the system upon engine shut-down. Finally, ecology fuel return systems can drain the combustor of any unused fuel upon engine shut-down thus preventing any smoke exhaust from the engine upon engine start-up and potentially causing some localized undesirable fuel-rich conditions in the combustor (i.e., “hot spots”).
Traditional ecology fuel return systems can sometimes experience instability. For example, there is a potential for air leakage into the aircraft's fuel system under some circumstances, such as negative G events that can occur during some flight maneuvers. The air entrained in the fuel could interfere with normal operation of the engines.
Such conventional methods and systems have generally been considered satisfactory for their intended purposes. However, there is still a need in the art for systems and methods that allow for improved ecology fuel return systems. The present invention provides a solution for these problems.